Prior to this invention, flexible couplings of the type described above have been widely used in various applications for coupling pipe or tube sections together in a fluid-conveying system. One such flexible coupling is shown in FIG. 1 of the drawings. Other representative teachings of prior couplings are found in U.S. Pat. Nos. 3,596,934 (issued to H. A. DeCenzo on Aug. 3, 1971), 3,540,758 (issued to J. Torres on Nov. 17, 1970), 4,150,847 (issued to H. A. DeCenzo on Apr. 24, 1979), 3,414,299 (issued to H. D. Roe on Dec. 3, 1968), 3,273,917 (issued to R. O. Chakroff on Sept. 20, 1966), 3,002,771 (issued to R. O. Chakroff on Oct. 3, 1961), 2,714,021, (issued to O. Froidevaux on July 26, 1955), 2,497,441 (issued to J. I. Detweiler on Feb. 14, 1950), 2,212,745 (issued to R. D. McIntosh on Aug. 27, 1940) and 739,707 (issued to W. R. Park on Sept. 22, 1903), as well as Australian Pat. Nos. 130,521 (published on Jan. 18, 1948) and 250,541 (published Jan. 19, 1961).
The prior coupling of FIG. 1 comprises a pair of coupling flanges which are received in a coupler sleeve and which are fixed one to each of the pipe sections to be coupled together. A pair of retainer nuts threaded on the coupler sleeve limit the outward displacement of the coupling flanges and thus retain them within the coupler sleeve. O-rings carried by the flanges are deformed against the inner periphery of the coupler sleeve to establish the leak-preventing seals around the flanges.
When the flanges of the FIG. 1 coupling assembly are aligned in the unpressurized state, the subsequent pressure loads (due to pressurized fluid within the coupling) and the resulting reactions are colinearly related so that no bending moment is imposed on the pipe sections or the flanges themselves. However, when one or both of the coupling flanges are initially misaligned, as commonly occurs in actual installations, an undesirable eccentricity or radial offset develops between the centrally-acting pressure loads and the displaced reactions to objectionable apply a bending moment to the interconnected pipe sections.
The radial offset between the pressure load and the reaction to the pressure load is shown for the right-hand flange in FIG. 1. It will occur because the right-hand flange is angularly misaligned with the coupling sleeve so that when the pressure load pushes the coupling flanges away from each other, the back shoulder of the right-hand flange engages the adjacent retainer nut at a localized region. The pressure loads will therefore be reacted at the localized contact region, thus resulting in a bending moment on the tubing or pipe section and the flange/tubing joint.
The spherical seating construction shown in FIG. 6 and elsewhere of the '934 DeCenzo patent appears to eliminate the pressure-induced bending on the interconnected pipe sections. However, like the prior coupling of FIG. 1, the DeCenzo coupling is susceptible to the pressure-induced extrusion of the elastically deformable seal ring into the clearance between the flange and the coupler sleeve.
In the DeCenzo coupling, the organization and connection of parts are such that the center of articulation for each coupling flange is located axially beyond the end face of each coupling flange. For example, the center of rotation or articulation is located at point "X" in the embodiments shown in FIGS. 1 and 6 of the '934 DeCenzo patent.
Because of the location of DeCenzo's center of articulation, the enlarged, seal-ring confining flange shoulder will swing through a substantial arc as the coupling flange is articulated. A relatively large, radial clearance is therefore required between DeCenzo's coupling flange and the coupling sleeve to permit sufficient articulation of the coupling flange. The larger the clearance between these parts, the greater will be the extrusion of the elastically deformable seal ring into the clearance under the influence of pressurized fluid within the coupling. Extrusion of the seal ring into the clearance may damage the seal ring or otherwise impair the seal between the coupling flange and the coupler sleeve.
Apart from the foregoing problems, none of the prior coupling teachings noted above addresses the problem of utilizing existing flanges of the type shown in FIG. 1 but yet avoiding the objectionable pressure-induced bending on the interconnected tube or pipe sections.